Janus-textured substrates refer to surfaces with heterogeneous topographies, which have received particular attention recently due to their potential application in manipulating droplet-bouncing behaviors [Li et al., Nat. Phys. 12, 606–612 (2016)]. In this paper, the droplet impact dynamics on the Janus-textured heated substrates are numerically investigated with an improved thermal lattice Boltzmann method. A comprehensive parametric study is conducted by varying the wettability, the Jakob number, the Weber number, and the surface topographies. With different control parameters, three distinct boiling regimes are observed, i.e., the contact boiling regime, the transition boiling regime, and the film boiling regime (Leidenfrost state). To reveal the underlying physics, the distributions of the unbalance Young's force, the thermophoretic force, and the vapor pressure difference in the system are theoretically analyzed. As for the self-propulsion behaviors, it is find that the droplet tends to move toward the denser side (area with more pillar arrays) for the contact boiling regime. However, when the droplet is under the Leidenfrost state, its bouncing dynamics depend on the combined effects of the Weber number and the wettability, and a decrease in wettability induces the droplet to migrate toward the sparser side (area with fewer pillar arrays). These physical insights enrich the fundamental understanding of the droplet-bouncing dynamics on heated substrates and also provide guidelines for designing advanced surfaces to manipulate the droplet-bouncing behavior.

The motion of a neutrally buoyant circular particle in a clockwise double-lid-driven square cavity is studied with the lattice Boltzmann method. To understand, predict, and control the motion of the circular particle, the effect of the initial position, particle size, and Reynolds number is studied. The center of the square cavity is a fixed point, where the circular particle remains stationary all the time; otherwise, the circular particle is stabilized at the limit cycle, which is created by the inertia of the circular particle, confinement of the boundaries of the square cavity, and vortex behavior. The effect of the particle size on the motion of the circular particle is obvious, with the increase in the particle size, the confinement of the boundaries becomes stronger, and the limit cycle shrinks toward the center of the square cavity. With the increase in the Reynolds number, the fluid flow becomes stronger, two symmetric secondary vortices at the top left and bottom right corners develop, and the limit cycle is squashed along the leading diagonal of the square cavity.

Particulate flows with thermal convection exist widely, and the lattice Boltzmann method is proved to be an accurate and efficient solver. Two issues are crucial, namely, the treatment of the velocity and temperature boundaries at the particle surface and the initialization of the fresh fluid nodes due to the movement of the particle. However, these two issues are treated separately, and the inconsistency decreases the numerical accuracy and stability. Thus, a consistent treatment of these two issues is presented, which includes the prediction and correction steps, and it is validated by four numerical experiments. The present method is of the second-order accuracy, and it provides a consistent treatment for particulate flows with thermal convection.

The flow in the square cavity with internal obstacles exists widely; thus, investigating the effect of the existence of the obstacles on the flow and the motion of the solid particles is important. To understand, predict, and control the motion of the solid particles, the motion of a neutrally buoyant circular particle in a lid-driven square cavity with an internal circular obstacle is studied with the lattice Boltzmann method, where the effects of the obstacle size, obstacle location, initial position of the circular particle, and Reynolds number are investigated. Under the effect of the obstacle, the flow and the motion of the particle are quite different. Especially, under some cases, no limit cycle is observed, and the particle is captured by the secondary vortex at the lower layer of the square cavity, which is insensitive to the initial position of the circular particle. The effect of the Reynolds number on the motion of the particle is significant, with the increase in the Reynolds number, and the motion of the particle is different obviously. At low Reynolds numbers, the motion of the particle is confined by the primary vortex, which moves along the limit cycle at the upper layer of the square cavity. With the increase in the Reynolds number, the effect of the inertia of the particle becomes stronger, and the particle moves from the primary vortex to the secondary vortex until it is captured by the secondary vortex. At relatively high Reynolds numbers, the primary vortex develops, and the particle is confined by the primary vortex again, forming another limit cycle.

Since geological structures around coal mines are complex, sudden coal mine water inflow is seriously threatening coal mining safety. To improve the accuracy of predicting coal mine water inflow, a multi-source dataset is collected to develop a coal mine water inflow prediction model based on multi-factor Pearson correlation analysis, where a convolutional neural network and bidirectional long short-term memory neural network are adopted to extract features from time-series data. To validate the performance of the present prediction model, a case study is conducted, where the predicted coal mine water inflow is close to the collected coal mine water inflow. Meanwhile, compared to other prediction models, the present prediction model can predict the magnitude and development trend of coal mine water inflow in the next 8 h more accurately, where the mean absolute percentage error is 5.76% and the correlation coefficient is 0.922.